Hydraulic driving device for clamping chucks and the like



y 1934- K. MILOTTA 7 1,968,700

HYDRAfiLi bRI vINe DEVICE FOR CLAMPING CHUCKS AND THE LIKE Filed May 4,1952 2 Sheets-Sheet 1 INVENTO R mm. mm.

INVENTOR 2 Sheets-Sheet 2 v K. MILOTTA July 31, 1934.

HYDRAULIC DRIVING DEVICE FOR CLAMPING CHUCKS AND THE LIKE Filed May 4, 1932 Patented July 31, 1934 7 HYDRAULIC DRIVING DEVICE FOR CLAMP- ING CHUCKS AND THE LIKE I Karl Milotta, Berlin, Germany Application May 4, 1932, Serial No. 609,206 In Germany May 9, 1931 6 Claims. (Cl. 279-4) With hydraulically driven clamping chucks it is requisite, in order to enable the hydraulic piston to hold the chuck properly fast in its closed position, that said piston exerts a comparatively high pressure, and its active surface must, therefore, be correspondingly large whereby a correspondingly large amount of the liquid under pressure is necessitated for moving the said piston, whereas, when the clamping fast has been ef- 10 fected or is no more necessary, which is the case during the greatest part of the time, only a slight amount of the liquid is requisite, viz. only so much as is necessary to make up for the loss by leakage. A consequence thereof is that, in order to be able to effect the clamping and the release in a certain proper period of time, a pump with a comparatively large performance must be employed which runs without load during the greatest part of the time whereby losses of energy are caused.

The object of the present invention is to obviate the just-mentioned drawback, and this object is attained by the provision of pistons, of which one is intended solely for the clamping and the releasing operation, whereas another which is larger than the first becomes active only at the end of the movement and serves for keeping the clutch in its state of clamping. This larger piston may have a passage through which the two chambers at the two sides of said piston com municate with one another so that while the clutch is operated by the small piston the liquid present in the chamber in front of the large piston can pass practically without friction into the chamber behind this piston and this chamber is, therefore, always filled with liquid and only a small amount of liquid need be supplied for effecting the final pressure.

Another object of the present invention is to 40 prevent the oil under pressure which is not required in the interim after the clamping and the release from flowing uselessly away through the pump, so that it is unnecessary to make use of a pump with variable output. For this pur- 45 pose the suction pipe of the pump is equipped with a control gear so designed as to be adapted to determine the amount of the liquid sucked in, and to be operated manually or automatically by the pressure existing in the pressure pipe.

The invention is illustrated diagrammatically and by way of example on the accompanying drawings on which Fig. 1 is a representation of the complete arrangement and combination of parts constituting my invention. Fig. 2 is an axial section through the driving means for the clamping chuck drawn to a greatly enlarged scale relatively to Fig. 1. Fig. 3 is a similar view and shows a modification of the invention. Fig. 4 is a clamping drive of another construction and Fig. '5 is a section through the regulating device, all as fully described hereinafter,

On the drawings, a denotes the shaft case of a machine tool equipped with a clamping chuck with hydraulic drive according to this invention.

b is the clamping chuck body, 0 is the hydraulic piston which is fixed on the rotating shaft. Opening and closing the chuck b is effected hydraulically. Supplying and withdrawing the fluid under pressure, for instance oil, takes place through tubes d and e, which extend from said body 12 to a changing-over casing j which is provided with a changing-over cock or valve g by means of which said pipes d and 6 can be connected alternately either with the pressure pipe h or with the discharge pipe is which latter terminates at the oil sump i. Conveying the oil or other liquid is effected by means of a prunp m which sucks the oil etc. from the sump through the suction pipe n and presses it into the pressure pipe 71. through a regulating device 0 which will 0 be fully described. From the pressure pipe h a pipe p branches off, the other end of which ter minates at the regulating device 0 and which serves for controlling this device, as will also be more fully described hereinafter.

The details of the clamping device and the driving means thereof are shown in Fig. 2. The two oil supply pipes 11 and e are connected with the casing by two threaded members 1 and 2 which are inserted into the stationary bearing part 3 of the piston.

The clamping clutch may consist, for instance, of a body 4 in which are supported bell-crank levers 5, one arm of each of which engages the clamping jaws 6 and moves them radially, where- 5 as the other arm of each of said levers engages a ring 7, by the axial shifting of which the clutch is moved into its clamping position, or is released. The ring 7 is located upon a hollow shaft or rod 8 through which the work-piece to be clamped 109 fast, for instance a rod or bar 1* is moved.

The axial movement of the hollow shaft 8 is effected hydraulically. This shaft is, for this purpose, firmly connected with a tube 8' (Fig. 2) designed as a hydraulic piston. A part 10 of the tube 8' is thicker than the other part and is surrounded with a cylindrical sleeve 11 which forms, together with said thicker part 10, a piston having an annular surface. This piston moves in a cylindrical space 12 provided in the cover 13 Ho of a cylinder 14. The space 12 is closed by a sleeve 15 which either is integral with the cover 13 or is connected with the same by a screw 16, as in the constructional form shown in the drawings by way of example.

In the cylindrical part 14 moves the main clamping piston proper 17 which engages the ring 11 with a projection 18. Upon the shoulder formed on the tube 8 by the thicker part 10 is provided a plate 19 which serves as support for a spring 20. The other end of the spring contacts with a collar 21 of the tube 8, and the spring, therefore, holds the piston 17 in its position relatively to the tube 8', which is the position shown in the drawings. The inner cylindrical part of the piston which encompasses the tube 8' has several bores 22 through which, in the position of the parts shown in the drawings, the chambers at the two sides of the cylinder 14 communicate with one another so that the liquid present in the one of said chambers can freely and practically without resistance flow over into the other of the said chambers.

That side of the piston 17 which lies opposite the collar 21 has a valve face 23 which can contact with a corresponding face 24 of the collar 21, when the spring 20 is compressed. In this case the chambers at the two sides of the cylinder 14 are closed with respect to one another. The tube 8' is thicker also behind the collar 21 and that thicker part 25 is followed by a part 26 having a somewhat smaller diameter. In this way there is again formed an annular piston which moves in a cylindrical space 27 formed in an extension of the bottom 28 of the cylinder 14. Said space 27 is closed by a sleeve 29 inserted into the bottom 28.

The manner of operation of the device is as follows:

When the rod or bar to be worked has been moved forwards as far as required, the chuck is closed by pulling the tubes 8 and 8'. The cock 9 for regulating the oil or other liquid under pressure is, at this time, so adjusted that the liquid under pressure is supplied through the pipe 6, from which it enters into the space 12 in the following manner: bores 30 and 31 provided in the cylinder bottom 28, a bore 32 provided in the cylinder itself; and another bore 33 which is provided in the cylinder cover and communicates with said space 12 through a bore 33a. The oil under pressure acts upon the thicker part 10 and the ring 11 and shifts the tube 8' to the left, the piston 17 being taken along with said tube. The oil present in the chamber in front of the piston, viz. lefthand from it, flows through the bore 22 to the other side of the piston without finding any resistance worth mentioning.

As soon as the work piece has been clamped fast in the clutch, the tube 8' comes to a standstill, but as the liquid in the cylinder 12 is still further active the piston 1'7 is shifted forwardly by the tube 11 against the action of the spring 20, which is now the only tube moved, the movement being continued until the intermediate space between the faces 23 and 24 has been bridged and these two faces contact with one another. By this way the chambers at the two sides of the piston are tightened with respect to one another. A small amount of oil etc. enters from the cylindrical space 12 through a very small by-pass 34 into the space at the right-hand from the cylinder 17 so that this space is subjected to the pressure, and this pressure which acts upon the entire sectional area of the cylinder 17 now holds the clutch in its clamped position.

When the clutch is released, the oil under pressure is supplied through the pipe d, whereas the pipe e is connected up to the discharge pipe. Owing thereto, the previously supplied oil can flow back, whereas the oil under pressure now flows into the annular space 27 where it moves the pipe 8' rearwardly. Owing to the relief of the space 12 the spring 20 can move the piston again into theposition shown in Fig. 2 and when the chuck is now opened, viz. when the tube 8' is shifted to the right, the oil present on the right hand side of the piston 17 can flow away unimpededly to the left-hand side through the apertures 22.

Fig; 3 shows another form of construction of the pressure cylinder. In this modification instead of the tube 11, a cylindrical projection 1111 has been provided on the cylinder cover 1341. projecting into a cylindrical recess 44 of the piston 17a. The piston is provided wn'th an inner flange 45 contacting the thicker part 10a of the cylindrical shaft 80,. Between the flange 45 and the projection 11a a chamber 44 is formed being connected by a channel 47 with the cylindrical chamber 48; as the construction otherwise fully corresponds with that shown in Fig. 2 for the other parts the same reference numerals are used as in Fig. 2. The oil flowing through the bore 33 will fill the chamber 48 and will flow through the channel 4'7 into the chamber 44 and then through the channel 44a into the piston chamber z. The air will be removed through the opening occupied by a screw 5 which, for this purpose, is loosened, and as soon as the chamber is filled with oil the screw is tightened and it then has no further use, except, of course, to close the opening and maintain it closed. It is to be assumed hereby that no pressure will be applied on the rod 8a since otherwise the valve plate 24 would close and the piston chamber would then be divided.

The manner of operation of this modification is as follows:

The liquid under pressure flows through the channels 31, 32 and 33 into the chamber 48 and from here through the channel 4'7 into the cylindrical chamber 44, where it presses against the flange 45 of the piston 17a. Hereby the clutch is closed in the manner described in connection with Fig. 2.

The modification shown in Fig. 4 shows another form of a clamping chuck consisting of a bushing 41 provided with two or three slots, there remaining, however, a. non-slotted annular portion 42, whereas the slotted main portion of the bushing or sleeve is outwardly conical and contacts here with the correspondingly shaped surfaces of the outer sleeve 43. The bushing 42 is screwed upon the shafts 8, so that when this shaft is moved in the one direction the jaws formed by said slots are pressed together in order to hold fast the work-piece 9. whereas when the said rod is moved in the other direction the jaws are released whereby also the work-piece is released.

As the periods of time during which the clutch is in operative state, or is released, are considerably longer than those periods of time in which the clutch is being brought into operative state, or is being released, these latter periods of time being those in which the piston is being moved, the pump delivering the oil or other liquid under pressure will run comparatively long without load and during these periods of time the conveyed oil will first be placed under pressure and then useless flow away. In order to obviate this useless work a regulating device has been provided. The device consists of a cylinder in which a small piston 70 can be moved. This piston has an annular groove 71 which is provided at such a place that when the piston is in its end-position (Fig. the pipe 11. which is connected with the oil sump and the pipe 73 which is connected with the pump terminate at it. The piston is subjected to the pressure of a spring '74 which tends to hold it in said end-position and the tension of which can be regulated by a manually operable adjusting screw '75. At the frontal side of the piston terminates into the cylinder the pipe 9 which is branched ofi from the pressure pipe. The spring '74 is normally so adjusted that it can just stand the pressure exerted upon the piston '70 by the liquid supplied through the pipe p; owing thereto, sucking of the liquid by and into the pump can take place inthe proper manner.

When the chuck has attained its operative state. and if, therefore, no considerable amount of the liquid under pressure is required, the liquid under pressure arriving through the pipe 9 will now shift the piston '70 in such a direction that the connection between the pipes n and 73 through the groove 71 of the piston '10 is narrowed. Owing thereto, only correspondingly less liquid can be sucked in so that the pump m is correspondingly relieved and requires therefore, correspondingly less power. 4

In order to prevent the pressure on the nonworking side of the piston 1'7 in the cylinder 14 to rise in an inadmissible degree by reason of leakages or other causes, whereby the proper operation of the chuck might be impaired, non-retum valves 35 and 36 are provided on both sides, preferably in the form of balls subjected to the action of springs 37 and 38.

I claim:

1. A hydraulic driving device for clamping chucks and the like, comprising a main movable piston and piston rod through which a work piece is adapted to be placed, said piston being movable relative. to its rod, means on the end of the piston rod to operate the chuck, a cylinder for the piston, and means combined with said cylinder and comprising a valve cooperating with the piston to render possible free passage of the liquid from the cylinder chamber at the one side of said piston into the chamber at the other side of said piston during the clamping action proper and the releasing action proper of the chuck, and to separate said cylinder chambers from one another when a movement of the piston relative to its rod after the clamping has taken place, so that the further supplied fluid serves to increase the pressure at one side of the said piston.

2. A hydraulic driving device according 'to claim 1, in which two auxiliary pistons are connected with the main piston and are subjected to pressure from the same source of pressure, said auxiliary pistons being adapted to shift the main piston during the clamping and the releasing action of the chuck.

3. A hydraulic driving device according to claim 1, in which the valve is adapted to be maintained open in its position of rest or during its movement while being relieved, and is closed at the end of the clamping movement by the increase of the pressure then taking place in one of the chambers of the cylinder.

4. A hydraulic driving device according to claim 1, in which the valve is adapted to be maintained open in its position of rest or during its movement while being relieved, by a spring, and is closed at the end of the clamping movement by the increase of the pressure then taking place in the cylindrical chamber between a projection of the bottom of the cylinder and a flange on the piston.

5. A hydraulic driving device acccsding to claim 1, in which non-return valves are provided to prevent a pressure in the chamber of the cylin der.

6. A hydraulic driving device according to claim 1, in which ,two auxiliary pistons are connected with the main piston of smaller sectional area and are subjected to, pressure from the same source of pressure, one of said smaller pistons being adapted to eflect the clamping movement, and the cylinder of the respective piston communicating with the cylinder of the main piston by a small orifice adapted to permit passage of liquid from said smaller cylinder into said larger one in order to increase the pressure therein.

, KARL MILO'I'I'A. 

